Did the Four Imams intend for their knowledge to become schools of thought, or did this classification occur later?

The four Imams and other Imams of Ijtihad (independent reasoning) followed the evidence and sought the Sunnah of the Prophet, peace and blessings be upon him. None of them founded an independent madhhab (school of thought); rather, they exercised Ijtihad according to their knowledge. Then came those after them who gathered their knowledge and disseminated it. Imam Ahmad, for instance, did not author works in Fiqh (Islamic jurisprudence); instead, Al-Khallal collected what was transmitted from him in "Al-Jami' Al-Kabir." The Imams themselves forbade people from blindly following them and commanded them to follow the texts, urging them to disregard their sayings if they contradicted the text.